/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.ui;

import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.springframework.core.Conventions;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Implementation of the {@link Model} interface based on a {@link ConcurrentHashMap}
 * for use in concurrent scenarios.
 *
 * <p>Exposed to handler methods by Spring WebFlux, typically via a declaration of the
 * {@link Model} interface. There is typically no need to create it within user code.
 * If necessary a handler method can return a regular {@code java.util.Map},
 * likely a {@code java.util.ConcurrentMap}, for a pre-determined model.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
@SuppressWarnings("serial")
public class ConcurrentModel extends ConcurrentHashMap<String, Object> implements Model {

    /**
     * Construct a new, empty {@code ConcurrentModel}.
     */
    public ConcurrentModel() {
    }

    /**
     * Construct a new {@code ModelMap} containing the supplied attribute
     * under the supplied name.
     *
     * @see #addAttribute(String, Object)
     */
    public ConcurrentModel(String attributeName, Object attributeValue) {
        addAttribute(attributeName, attributeValue);
    }

    /**
     * Construct a new {@code ModelMap} containing the supplied attribute.
     * Uses attribute name generation to generate the key for the supplied model
     * object.
     *
     * @see #addAttribute(Object)
     */
    public ConcurrentModel(Object attributeValue) {
        addAttribute(attributeValue);
    }


    @Override
    public Object put(String key, Object value) {
        if (value != null) {
            return super.put(key, value);
        }
        else {
            return remove(key);
        }
    }

    @Override
    public void putAll(Map<? extends String, ?> map) {
        for (Map.Entry<? extends String, ?> entry : map.entrySet()) {
            put(entry.getKey(), entry.getValue());
        }
    }

    /**
     * Add the supplied attribute under the supplied name.
     *
     * @param attributeName  the name of the model attribute (never {@code null})
     * @param attributeValue the model attribute value (ignored if {@code null},
     *                       just removing an existing entry if any)
     */
    public ConcurrentModel addAttribute(String attributeName, @Nullable Object attributeValue) {
        Assert.notNull(attributeName, "Model attribute name must not be null");
        put(attributeName, attributeValue);
        return this;
    }

    /**
     * Add the supplied attribute to this {@code Map} using a
     * {@link org.springframework.core.Conventions#getVariableName generated name}.
     * <p><i>Note: Empty {@link Collection Collections} are not added to
     * the model when using this method because we cannot correctly determine
     * the true convention name. View code should check for {@code null} rather
     * than for empty collections as is already done by JSTL tags.</i>
     *
     * @param attributeValue the model attribute value (never {@code null})
     */
    public ConcurrentModel addAttribute(Object attributeValue) {
        Assert.notNull(attributeValue, "Model attribute value must not be null");
        if (attributeValue instanceof Collection && ((Collection<?>) attributeValue).isEmpty()) {
            return this;
        }
        return addAttribute(Conventions.getVariableName(attributeValue), attributeValue);
    }

    /**
     * Copy all attributes in the supplied {@code Collection} into this
     * {@code Map}, using attribute name generation for each element.
     *
     * @see #addAttribute(Object)
     */
    public ConcurrentModel addAllAttributes(@Nullable Collection<?> attributeValues) {
        if (attributeValues != null) {
            for (Object attributeValue : attributeValues) {
                addAttribute(attributeValue);
            }
        }
        return this;
    }

    /**
     * Copy all attributes in the supplied {@code Map} into this {@code Map}.
     *
     * @see #addAttribute(String, Object)
     */
    public ConcurrentModel addAllAttributes(@Nullable Map<String, ?> attributes) {
        if (attributes != null) {
            putAll(attributes);
        }
        return this;
    }

    /**
     * Copy all attributes in the supplied {@code Map} into this {@code Map},
     * with existing objects of the same name taking precedence (i.e. not getting
     * replaced).
     */
    public ConcurrentModel mergeAttributes(@Nullable Map<String, ?> attributes) {
        if (attributes != null) {
            attributes.forEach((key, value) -> {
                if (!containsKey(key)) {
                    put(key, value);
                }
            });
        }
        return this;
    }

    /**
     * Does this model contain an attribute of the given name?
     *
     * @param attributeName the name of the model attribute (never {@code null})
     * @return whether this model contains a corresponding attribute
     */
    public boolean containsAttribute(String attributeName) {
        return containsKey(attributeName);
    }

    @Override
    public Map<String, Object> asMap() {
        return this;
    }

}
